Cover, A Container Assembly Including The Cover, A Molding Device For Molding The Cover And A Method For Manufacturing The Cover

ABSTRACT

A cover for covering an opening of a container for a food stuff includes a substantially flat cover body including at least one aperture and at least one substantially flat flap. The at least one flap including a linear proximal end configured to connect with the cover body and allow the at least one flap to rotate with respect to the cover body. A lower surface of the at least one flap includes a protrusion configured to close the at least one aperture when the at least one flap is at a first position in which the at least one flap is in parallel with the cover body. The cover body and the at least one flap are integrally formed by a co-injection molding. The container and cover are suitable for heating a food stuff in a microwave.

CROSS REFERRENCE TO RELATED APPLICATIONS

This application is a division of co-pending U.S. patent applicationSer. No. 12/384,975, filed on Apr. 10, 2009 by the same inventor, whichis a continuation, as authorized by 35 U.S.C. §365(c), of InternationalApplication No. PCT/JP2007/069867, filed on Oct. 11, 2007, which claimspriority of Japanese Patent Application No. 2006-280237, filed on Oct.13, 2006, the entire content and disclosure of the precedingapplications are incorporated by reference into this application.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a container assembly for a food stuff and acover thereof. Further, this invention relates to the container assemblyand the cover suitable for cooking a food stuff therein with a heatingdevice such as a microwave.

2. Description of the Related Art

A container assembly comprising a container for a food stuff and a coverfor covering an opening on a top of the container is often used in adaily life, for example, as a container assembly may contain a foodstuff and then may be placed in a refrigerator for storage of the foodstuff, or may be used as a lunch box.

It is advantageous that such a container assembly is repeatedly used. Anexemplary preservation/storage may be to cover a food stuff in a bowlwith a resin film and place the bowl in a refrigerator. This exemplarypreservations/storage essentially requires waste of the resin film afterits usage. On the other hand, the above mentioned container with thecover may not produce any waste.

In general, the cover of the container assembly for the food stuff mayhygienically seal the container assembly. When the food stuff in thecontainer assembly is microwaved, the cover has to be removed from thecontainer. This is because an increase in an inner pressure of thecontainer assembly during heating process due to an airtight sealing bythe cover attached to the container may blow out the cover or destroythe container.

Japanese Patent No. 3513599 discloses a container assembly useful forsolving the above-described inconvenience in use. FIG. 14 is a schematicperspective view of the container assembly disclosed in Japanese PatentNo. 3513599. FIG. 15 is a longitudinal cross-sectional view of thecontainer assembly shown in FIG. 14.

A container assembly (C) in FIG. 14 and FIG. 15 includes a container (B)and a cover (L). The container (B) for a food stuff is configured tohave a bottom and side walls surrounding the bottom. The cover (L)covers an opening at a top of the container (B).

The cover (L) comprises a central area (M) and a peripheral area (P).The central area (M) and the peripheral area (P) connected each otherare molded through a double-molding process.

The central area (M) includes an aperture (O). The peripheral area (P)connects with a flap (F). The flap (F) extends to a center of the cover(L) from the peripheral area (P). The protrusion (S) extendingdownwardly is formed on a bottom of the flap (F).

The flap (F) rotates upwardly and downwardly with respect to a proximalend (A) connecting with the peripheral area (P). When the flap (F) is inparallel with the top of the cover (L) by its downward rotation, theprotrusion (S) engages with and closes the aperture (O) defined in thecover (L).

A container assembly (C) in FIG. 14 and FIG. 15 does not require toremove the cover (L) when heating the food stuff therein, because a thecontainer assembly (C) may be capable of exhausting a water vapor fromthe food stuff or inflating air therein so as to avoid an excessiveinner pressure.

Thus, the container assembly (C) in FIG. 14 and FIG. 15 can overcome theabove-described inconvenience when in use.

The container assembly disclosed in Japanese Patent No. 3513599 has adisadvantage of high production cost although it has a superior featureto overcome the conventional inconvenience when in use, because thecover (L) is manufactured through the double-molding process whichrequires many process steps.

FIG. 16 shows a container assembly (C) which overcomes the expensiveproduction cost caused by the double-molding process.

The container assembly (C) in FIG. 16 is substantially similar to aconfiguration of the container assembly (C) described relating to FIG.14 and FIG. 15 except for a joint structure between the flap (F) and thecover (L) by an assembly process.

Thus, the flap (F) and the cover (L) are individually molded through aresin-molding process, and then integrally jointed each other throughthe assembly process.

The container assembly (C) in FIG. 16 can be manufactured without acomplicated process such as the double-molding process. However, theassembly process is still required, therefore reduction in themanufacturing cost may not be enough.

Further, the container assembly (C) in FIG. 16 has another problem. Theflap (F) and the cover (L) are originally separate components althoughthey are integrated through the assembly process. During long usage, theflap (F) happens to drop off the cover (L). A reattachable configurationof the flap (F) may somehow overcome the above-described problem, but ifthe flap (F) is lost after dropping off, the container assembly is nolonger reparable.

In order to solve the problems described above, the present inventionprovides a cover which can be manufactured without any complicatedmanufacturing processes. The present invention further provides a coverfrom which a flap does not fall. The present invention also provides acontainer assembly using the cover described above.

SUMMARY OF THE INVENTION

The present invention provides a cover for covering an opening of acontainer for a food stuff comprising: a substantially flat cover bodyincluding at least one aperture at least one substantially flat flapincluding a linear proximal end configured to connect with the coverbody, the proximal end allowing the at least one flap to rotate withrespect to the cover body, wherein a lower surface of the at least oneflap includes a protrusion configured to close the at least one apertureof the cover body when the at least one flap is at a first position inwhich the at least one flap is in parallel with the cover body, thecover body and the at least one flap are integrally formed by aco-injection molding.

In one embodiment of the present invention, the proximal end of the atleast one flap is located farther away from a center of the cover bodythan a distal end of the flap.

In another embodiment of the present invention, the proximal end of theflap is located closer to the center of the cover body than the distalend of the flap.

Yet in another embodiment of the present invention, the at least oneaperture is formed in a vicinity of a periphery of the cover.

In another embodiment of the present invention, the cover is contouredin a multangular shape, and the at least one aperture is located in avicinity of a corner of the cover.

In another embodiment of the present invention, the cover body includesa downward concave portion, a distal end of the flap partly covers overthe concave portion when the at least one flap is at the first position.

In another embodiment of the present invention, the lower surface of theflap at the proximal end includes a groove with an arc cross section,and the groove and a flat upper surface of the flap appear when the atleast one flap is at a second position in which the at least one flapstands uprightly to the cover body, so as to restrict an upward rotationof the flap up to the second position.

In another embodiment of the present invention, the cover body comprisesa reception configured to receive the at least one flap when the atleast one flap is in the first position, an upper surface of the atleast one flap does not protrude over an upper surface of the coverbody.

In another embodiment of the present invention, the cover is notdeformed under a thermal condition less than 140 degrees centigrade.

In another embodiment of the present invention, the cover is molded froma high crystallinity polypropylene.

In another embodiment of the present invention, the at least oneaperture comprises a plurality of the apertures in the cover body.

Another embodiment of the present invention further comprises a tabprotruding outwardly from a peripheral edge of the cover.

The present invention further provides a container assembly for a foodstuff comprising a container including a bottom and at least one sidewall surrounding the bottom, and a cover for closing an opening of thecontainer, wherein the cover comprising: at least one substantially flatcover body including a linear proximal end configured to connect withthe cover body, the proximal end allowing the at least one flap torotate with respect to the cover body; a protrusion configured to closethe at least one aperture of the cover body when the at least one flapis in the first position where the at least one flap is in parallel withthe cover body, the cover body and the at least one flap are integrallyformed by a co-injection molding.

In another embodiment of the present invention, the cover comprises: aperipheral area defining a peripheral contour of the cover; a flapsurrounding area at least partly surrounding the at least one flap; andan intermediate area configured to connect the peripheral area with theflap surrounding area so that an upper surface of the peripheral areaand an upper surface of the flap surrounding area are located above anupper surface of the intermediate area; the bottom of the containercomprises: a peripheral area defining a peripheral contour of thebottom; and a central area at least partly surrounded by the peripheralarea of the container, so that a bottom surface of the central area islocated above a bottom surface of the peripheral area, the intermediatearea is configured to at least partly engage with the peripheral area ofthe container while the central area is configured to engage with theflap surrounding area in a stacking package of the container assemblies.

In another embodiment of the present invention, the peripheral area ofthe cover body is formed to have a U-shaped cross section so as to beengageable with an upper edge of the container.

In another embodiment of the present invention, the cover is formed in acylindrical shape comprising a top and a threaded inner surface, whereina threaded outer surface of an upper portion of the container engageswith the threaded inner surface of the cover.

In another embodiment of the present invention, the cover is formed in adisc shape of which outer surface is threaded, wherein a threaded innersurface of an upper portion of the container assembly engages with thethreaded outer surface of the cover.

In another embodiment of the present invention, the at least one flaprotates upwardly from the first position when an inner pressure of thecontainer assembly is greater than a predetermined pressure.

In another embodiment of the present invention, a partition configuredto divide an inner space of the container into at least twocompartments, wherein the at least one aperture is in fluidcommunication with each of the at least two compartments, and the atleast one flap closes the at least one aperture is in fluidcommunication with each of the at least two compartments.

The present invention further provides a molding device for molding acover including a substantially flat cover body with at least oneaperture, and at least one substantially flat flap including a linearproximal end configured to connect with the cover body and a protrusionconfigured to close the at least one aperture of the cover body when theat least one flap is in the first position where the at least one flapis in parallel with the cover body, the proximal end allowing the atleast one flap to rotate with respect to the cover body comprising: afixed mold and a moveable mold configured to form a first cavitytherebetween for molding the cover body, the fixed mold including asecond cavity for molding the at least one flap, the second cavitycommunicating with and extending perpendicularly to the first cavity,wherein the fixed mold comprises: a lateral sliding block including amolding surface configured to mold at least one flap surface including aprotrusion is biased toward a protruding direction of the protrusion ofat least one molded flap, a vertical sliding block including a slopesurface complementary to and adjacent to a slope surface of the lateralsliding block opposite to the molding surface, a longitudinal movementof the vertical sliding block causing the lateral movement of thelateral sliding block in a protruding direction of the protrusion.

The present invention further provides a method for molding a coverincluding a substantially flat cover body with at least one aperture,and at least one substantially flat flap including a linear proximal endconfigured to connect with the cover body and a protrusion configured toclose the at least one aperture of the cover body when the at least oneflap is at the first position in which the at least one flap is inparallel with the cover body, the proximal end allowing the at least oneflap to rotate with respect to the cover body using a molding deviceincluding a moveable mold and a fixed mold, the fixed body including alateral sliding block including a molding surface configured to mold atleast one flap surface including a protrusion is biased toward aprotruding direction of the protrusion of at least one molded flap, anda vertical sliding block including a slope surface complementary to andadjacent to a slope surface of the lateral sliding block opposite to themolding surface forming a contour of the surface on which the protrusionis formed includes the slope surface causing the lateral movement of thelateral sliding block in the protruding direction of the protrusionformed in the at least one flap of the molded cover, comprising: forminga first cavity between the fixed mold and the moveable mold for moldingthe substantially flat cover body, so that the first cavity communicateswith a second cavity inside the fixed mold for molding the at least oneflap, injecting a molten resin into the first and the second cavity tomold the cover; and separating the moveable mold from the fixed mold inan open position to remove the molded cover.

A cover of the present invention is configured to exhaust a water vaporfrom a food stuff or an inflating air in a container assembly through atleast one aperture by upwardly rotating a flap (e.g. when heating thefood stuff inside the container assembly). Therefore, the cover does nothave to be removed from the container when heating. Further, the foodstuff in the container assembly may be hygienically stored (for example,in a refrigerator) by engaging a protrusion of the flap with theaperture of the cover body after rotating the flap downwardly.

The cover body and the at least one flap are formed by a co-injectionmolding without requiring any complicated additional process such as adouble-molding process or an assembly process. Further, the flap doesnot drop off the cover. An attempt to mold the cover including the atleast one flap by the co-injection molding has not been made due to thecomplicated shape of the cover. However, thanks to many researches for aresin-molding mold by the present inventors, the flap and the cover canbe molded by the co-injection molding, i.e. by injecting a molten resininto a cavity defining the cover body and a flap standing uprightly withrespect to the cover body.

A location or direction of the flap of the present invention is notlimited. For example, the configuration of the container assemblydescribed relating to FIG. 14 and FIG. 15, the flap location is limitedto a peripheral area, and a directional vector from a proximal end to adistal end of the flap has to be always oriented to a center of thecover. In the present invention, on the other hand, the flap and thecover body are molded through a co-injecting molding process, so thatthe flap can be molded at any desired position on the cover body. Thus,the flap can be provided in a central area or a vicinity of theperiphery of the cover body. The directional vector from a proximal endto a distal end of the flap may be directed to the center from theperiphery of the cover, or to the periphery from the center of thecover.

When the aperture, which is configured to be closed with the protrusionof the flap, is defined in the central area of the cover body, the watervapor from the food stuff or an inflating air inside the containerassembly can be effectively exhausted therefrom. When the aperture isdefined in a vicinity of the peripheral area of the cover body withplacing the flap so that the flap directional vector from the proximalend to the distal end is oriented to the center of the cover, the liquid(water) in the container assembly may be discharged through the apertureafter cooking. Consequently, the container assembly of the presentinvention is suitably used when cooking pasta or the like.

Further in the present invention, a number of aperture or flap of thecover body is not limited. When the container is divided by a partitioninto at least two compartments, the cover may include a plurality ofapertures so that each aperture is in fluid communication with eachcompartment. The position of the flap may be determined depending on thelocation of the aperture.

A shape in a plain view of the cover and the container assembly of thepresent invention can be properly selected by a user's demand, forexample, circle, oval, triangle, rectangular and other polygonal shapes.

It is preferable to define the concave portion below the distal end ofthe flap closing the aperture. Therefore, the distal end of the flap maylaterally and partly protrude across a top of the concave portion tofacilitate engagement with a user's finger and an upward rotation of theflap.

When the flap rotates upwardly until it stands uprightly to the coverbody, a groove with an arc cross section appears in a lower surface ofthe flap at the proximal end. On the other hand, a flat upper surface ofthe flap appears behind the groove. This configuration limits an upwardrotation of the flap from a parallel to an upright position with respectto the upper surface of the cover body. Thus, an excess repeated bendingstress on the proximal end of the flap can be avoided so that a life(usable period) of the cover may be extended.

The cover body is preferably provided with a concave area in which thetop of the flap is configured not to protrude from that of the coverbody when the flap rotates downwardly to engage the protrusion with theaperture of the cover body. Thus, another container assembly can bestably stacked on the cover.

In order to stably stack the container assemblies according to thepresent invention, the cover may include a peripheral area defining aperipheral contour of the cover, a flap surrounding area at least partlysurrounding the flap and an intermediate area therebetween from whichthe peripheral area and the flap surrounding area are elevated. Thus,one container assembly of the present invention can be stably stacked onanother container assembly.

The cover and the container of the present invention are molded from aresin which is not deformed under a thermal condition less than 140degrees centigrade, more preferably, they are molded from a highcrystallinity polypropylene.

Thus, cover and the container assembly molded from the above-describedresin may have a heat resistance comparable to a resin film used for amicrowave cooking A dish dryer may be applicable to the cover and thecontainer because they are dishwasher-safe. Further, the highcrystallinity polypropylene resin may increase an acceptable rotationalrepetition (a number of repetition of the flap rotation until theproximal end of the flap breaks).

The cover of the present invention may comprise a tab protrudingoutwardly from its peripheral edge from the container.

The method for fixing the cover to the container is not limited. Forexample, the peripheral area of the cover body may be formed to have aU-shaped cross section so as to be engageable with an upper edge of thecontainer. Alternatively, the threaded cover engages with the threadedcontainer. When the container and the cover are threaded, the cover isnot blown off due to increased inner pressure in the container assembly.When the inner pressure of the container assembly increases more than acertain pressure, the flap upwardly rotates so that a gas inside thecontainer is released from the aperture of the cover body. Thus, thecontainer assembly of the present invention is suitably used for acooking under a high pressure.

The present invention further provides a molding device and amanufacturing method for manufacturing a cover and a container assemblyincluding the cover having the above-described advantages.

BRIEF DESCRIPTION OF THE DRAWINGS

Hereinafter, the preferred embodiments of a cover and a container usingthereof according to the present invention are explained by referring todrawings.

FIG. 1 is an exploded perspective view showing the container assembly ofthe present invention.

FIG. 2 is a plane view of the cover the container of the presentinvention.

FIG. 3 is an enlarged cross-sectional view around the flap of the covershown in FIG. 2.

FIG. 4 is a further enlarged view to show of the proximal endconfiguration of the cover shown in FIG. 2.

FIG. 5 is a cross-sectional view of the cover shown in FIG. 2.

FIG. 6 is a schematic cross-sectional view of the resin-molding mold forthe cover shown in FIG. 2.

FIG. 7 is an enlarged view to show detail configuration of the mold inFIG. 6.

FIG. 8 is an exploded perspective view showing another embodiment of thecover of the present invention.

FIG. 9 is an exploded perspective view showing another embodiment of thecontainer of the present invention.

FIG. 10 is a plain view showing another embodiment of the cover used forthe container of the present invention.

FIG. 11 shows another embodiment of the container of the presentinvention.

FIG. 12 is an exploded perspective view showing another embodiment ofthe container of the present invention.

FIG. 13 is a cross-sectional view showing the stacked container of thepresent invention.

FIG. 14 is a perspective view of the conventional container assembly.

FIG. 15 is a cross-sectional view of the conventional containerassembly.

FIG. 16 is a perspective view of the conventional container assembly.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is an exploded perspective view of the container assembly of thepresent invention. FIG. 2 is a plain view of the cover of the presentinvention.

A container assembly (1) comprises a cover (2) and a container (3). Thecontainer (3) has a substantially rectangular cylindrical shape shown inFIG. 1 but not limited to this. It may also have a cylindrical/ovalcylindrical shape comprising a bottom, or a triangular cylinder or otherpolygonal shape. The container (3) contains a desired food stuff. Acouple of ears (31) extending from peripheral edges of the container (3)in parallel to each other are configured to facilitate carriage/handlingof the container assembly (1).

The cover (2) is configured to have a shape and a size for covering atop opening of the container (3), and an example in FIG. 1 and FIG. 2shows a substantially rectangular cover (2) similar to a contour of thecontainer (3).

A cover (2) includes a cover body (21) and a flap (22). The cover body(21) comprises a peripheral area (211) defining an outer peripheralcontour of the cover, a flap surrounding area (212) at least surroundingthe flap (22) and an intermediate area (213) therebetween configured toconnect these areas (211, 212). In FIG. 1 and FIG. 2, the flapsurrounding area (212) is provided at a center of the cover body (21),but it may be also adjacently provided to the peripheral area (211).

In the example in FIG. 1 and FIG. 2, the peripheral area (211) and theflap surrounding area (212) may be elevated upwardly with respect to theintermediate area (213). Further, the peripheral area (211) may behigher than the flap surrounding area (212). In addition, a tab (214)protruding outwardly from a peripheral area (211) is formed in asubstantially semicircle shape configured to facilitate detachableengagement with the container (3).

The flap (22) is a substantially semi-oval thin plate comprising alinear proximal end (221). The linear proximal end (221) of the flap(22) connects with the periphery of the flap surrounding area (212). Theflap (22) rotates upwardly and downwardly around the proximal end (221).

A protrusion (222) is formed in a bottom of the flap and an aperture(121) is defined in the flap surrounding area (212). After the flap (22)rotates downwardly until the flap (22) is in parallel with a top surfaceof the flap surrounding area (212), the protrusion (222) closes theaperture (121).

FIG. 3 is a cross-sectional view showing a configuration of the cover(2) around the flap (22). FIG. 3( a) is a cross-sectional view of theflap (22) standing uprightly with respect to the cover body (21) afterrotating the flap (22) upwardly. FIG. 3( b) is a cross-sectional view ofthe flap (22) in parallel with the top surface of the cover body (21) bya downwardly flap rotation.

The flap surrounding area (212) includes a downward concave area (122)and a deeper concave portion (123) adjacently provided thereto. When theflap (22) is downwardly rotated and a top surface of the flap (22) is inparallel with the top surface the cover body (21), a curved distalportion (224) of the flap (22) partly covers over the concave portion(123) so that it laterally extends an upper portion of the concaveportion (123). The rest of the flap portion (22) other than the distalportion lies in the concave area (122).

The aperture (121) is formed in the concave area (122). When the flap(22) is downwardly rotated until the top surface of the flap (22) is inparallel with the top surface of the cover body (21), a projection ring(223) formed surrounding a periphery of the protrusion (222) engageswith a bottom surface of the cover (2) so that a leveled position of theflap top surface with respect to the top surface of the flap surroundingarea (212) surrounding the concave area (122) is fixedly kept.

A user may insert his/her finger into the concave portion (123) definedin the flap surrounding area (212) for accessing the flap bottom (22) inorder to rotate upwardly. In addition, when the protrusion (222) plugsthe aperture (121), the top surface of the flap does not protrude overthe top surface of the flap surrounding area (212). Therefore, anothercontainer can be easily stacked on the container assembly (1), forexample, in the refrigerator.

FIG. 4 is an enlarged cross-sectional view of the proximal end (221) ofthe flap (22). At the proximal end (221) of the flap (22), a groove(226) with an arc cross section is defined in a flap bottom (225)(referred herein to a lower surface of the flap (22) after its downwardrotation). The groove (226) appears when the flap (22) stands uprightlyto the cover (2) while a flat upper surface (227) of the flap appearsbehind the groove (226). The groove (226) facilitates the flap rotationwhile the flap top (227) at the upright position prevents further upwardrotation of the flap (22) so that a rotation range is controlled between0 degree (the flap (22) lies on the cover (2)) and 90 degrees (the flap(22) uprightly stands to the cover (2)).

When the flap (22) is downwardly rotated, the proximal end (221) of theflap (22) is bent around a deepest bottom line (261) of the groove(226).

FIG. 5 is a cross-sectional view of the cover (2). The peripheral area(211) defining the outer contour of the cover (2) surrounds and upwardlyprotrudes to the intermediate area (213). An upper edge of theperipheral area (211) is provided above the top surface of the flapsurrounding area (212).

As shown in FIG. 5, the peripheral area (211) is formed to have asubstantially U-shaped cross section so as to engage with an upper edgeof the container (3).

FIG. 6 shows a shape of a cavity of a molding device for molding thecover (2).

The molding device comprises a fixed mold (41) and a moveable mold (42)configured to form a first cavity (45) therebetween for molding thecover body (21) of the cover (2). The fixed mold also includes a secondcavity (46) for molding the flap (22). The second cavity (46)communicates with the first cavity between the fixed mold (41) and themoveable mold (42). Further, an injection portion (43) for injecting amolten-resin is provided with the fixed mold (41).

As clearly shown in FIG. 6, the second cavity (46) is configured tostand at a right angle with respect to the first cavity (45). Thecavities (45, 46) make it possible to integrally mold the flap (22) andthe cover body (21) with a co-injection molding as the molten resinsurely flows into the second cavity (46) for molding the flap (22)through the first cavity (45).

FIG. 7 shows a configuration of the molding device shown in FIG. 6around the second cavity (46) for a flap (22), wherein the moldingdevice is in an open position after a molten-resin injection.

The fixed mold (41) comprises a lateral sliding block (411) including amolding surface configured to mold flap surface including a protrusion.A slope surface is opposite to the molding surface of the lateralsliding block (411), which is biased toward a protruding direction ofthe protrusion (222) by a biasing means such as a spring (not shown).

The fixed mold (41) further comprises a vertical sliding block (412)adjacent to a slope surface of the lateral sliding block (411). Thevertical sliding block (412) includes a substantially right trapeziumcross section. A slope surface of the vertical sliding block (412) iscomplementary to and adjacent to the slope surface of the lateralsliding block (411). An actuator (not shown) such as a cylinder connectsto the vertical sliding block (412) to move upwardly and downwardly.

During molding the cover (2), the vertical sliding block (412) is at alower limit position where a bottom of the vertical sliding block (412)to a top of the protrusion (421) upwardly protruding from a cavitysurface of the moveable mold (42) to penetrate the first cavity (45).The protrusion (421) defines the aperture (121) of the cover (2).

The vertical sliding block (412) moves upwardly in an opening operationof the molding device. The lateral sliding block (411) is biased to theslope surface of the vertical sliding block (412) by the biasing meansso that a vertical movement of the vertical sliding block (412) causes alateral movement of the lateral sliding block (411) (in a protrudingdirection of the protrusion (222)) to be separated from the molded flap(22). Thus, the protrusion (222) of the molded flap (22) is completelyseparated from the lateral sliding block (411). Then, the moveable mold(42) is moved downwardly so that the molded cover (2) is removed fromthe fixed mold without any interference with the protrusion (222) of theflap (22).

The type of the molten resin injected from the injection portion (43) isnot limited but it is preferable to have a heat resistance high enoughfor the cover (2) not to deform under a thermal condition less than 140degrees centigrade, because the container assembly (1) of the presentinvention may be used in a cooking device such as a microwave. A highcrystallinity polypropylene may be a preferable material, for example.Even after an endurance test in which the flap (22) of the cover (1)molded from the high crystallinity polypropylene was repeatedly rotatedbetween an open position and a closed position (more than 3,000 times ofrepeated rotation of the flap (22)), the flap (22) did not break out.

FIG. 8 is a perspective view of a modified embodiment from the containerassembly (1) in FIG. 1 to FIG. 6.

The container assembly (1) in FIG. 8 is formed with a plurality of theprotrusions (222) (3 protrusions in FIG. 8) with the flap (22). Thecover body (21) is also formed with the plurality of apertures (121)corresponding to the protrusions (222). When the flap (22) is rotateddownwardly, the protrusions (222) engage with the correspondingapertures (121), respectively. Therefore, apertures (121) are capable ofexhausting a larger volume of inflating gas in the container assembly(1) in heating.

FIG. 9 is a perspective view of another modified embodiment from thecontainer assembly (1) in FIG. 1 to FIG. 6.

The container assembly (1) in FIG. 9 comprises a plurality of the flaps(22) (2 flaps in FIG. 9). Each flap (22) configured to face each otherextends toward the center of the flap surrounding area (212). The flapsurrounding area (212) is formed with the concave areas (122) and theconcave portions (123) provided for each flap (22). Each flap (22)comprises the protrusion (222) and the concave area (122) is formed withthe aperture (121) engaging with the protrusion (222). The configurationof the concave area (122), the concave portion (123), the protrusion(222) and the aperture (121) are the same as what is explained relatingto the FIG. 1 to FIG. 6.

The container (3) includes a partition (32) configured to divide aninner space of the container into at least two compartments (33, 34).The apertures (121) are in fluid communication with the compartments,respectively when the cover (2) is attached to the container (3).

Generally, a volume of water vapor depends on a type of a food stuff tobe heated. Thus, a concentration of the water vapor in the spaces (33,34) of the container (3) may be different from each other during aheating process if every space (33, 34) contains a different food stuff,which leads to an inner pressure difference between the inner spaces(33, 34).

For example, if just one aperture (121) is provided on a cover (2) (likethe container assembly (1) described in context with FIG. 1 to FIG. 6),the aperture (121) may communicate with either of the spaces (33, 34).In a closed space, with which the aperture (121) does not communicate,an inner pressure will rapidly and extremely go up as a temperatureelevation compared with that in an open space with which the aperture(121) communicates, which may result in blowing of the cover fromcontainer (3).

As shown in FIG. 9, the container (3) having a plurality of theapertures (121) in fluid communication with each space (33, 34) and aplurality of the flaps (22) including the protrusions (222) which closethe apertures (121) prevents the cover (2) from being blown off becausethe inflating gas can be surely exhausted from each space (33, 34).

FIG. 10 is a plain view of the modified embodiment from the cover (2)shown in FIG. 1 to FIG. 6.

The flap (22) of the cover (2) shown in FIG. 10 is adjacently providedin the peripheral area (211) of the cover body (21). The flap (22) issurrounded by the flap surrounding area (212).

The flap surrounding area (212) in FIG. 10 is a substantiallyrectangular shape of which one of corners is adjacent to one of cornersof the substantially rectangular peripheral area (211). A couple of theedges of the flap surrounding area (212) defining its corner adjacent toa corner of the peripheral area (211) is coincident with the border ofthe peripheral area (211).

The aperture (121) is defined around the corner of the flap surroundingarea (212) adjacent to the corner of the peripheral area (211). Theflaps (22) are also provided with the protrusions (222) closing theaperture (121).

The proximal end (221) of the flap (22) is located more inwardly to thecenter of the cover than its distal end. The peripheral area (211) andthe flap surrounding area (212) are elevated with respect to theintermediate area (213) connecting these areas (211, 212). The distalend of the flap (22) protrudes to a valley formed with 2 adjacent slopesof the peripheral area (211) and the flap surrounding area (212). Thus,the embodiment in FIG. 10 does not have the concave portion (123) in thecover (2) as shown in FIG. 1 to FIG. 6, but only the concave area (122)receiving the flap (22).

Therefore, the container assembly (1) can discharge the liquid (water)generated from the food stuff therein through the aperture (121) definedat the corner of the cover (2).

FIG. 11 shows a modified embodiment from the cover (2) in FIG. 10. FIG.11( a) is a plain view of the cover (2) and the FIG. 11( b) is across-sectional view of the container assembly (1) to which the cover(2) in FIG. 11( a) is attached.

The cover (2) in FIG. 11 is formed in a cylindrical shape comprising atop and the aperture (121) is formed in a vicinity of the periphery ofthe cover (2). The cover (2) includes the flap (22) of which the distalend outwardly extends from the outer edge of the cover body (21). Theflap (22) includes the protrusion (222) which closes the aperture (121)when the flap (22) is downwardly rotated.

An inner surface of the cover (2) and an upper outer surface of thecontainer (3) are threaded.

The container assembly (1) in FIG. 11 is, for example, suitably used forcooking noodles such as pasta through the following steps:

a) put the dried pasta in the container (3) then pour hot water;b) cover the container with cover (2) and rotate the flap (22) upwardly;c) put the container assembly (1) in the microwave and boil the pasta inthe container assembly (1); andd) after the pasta is boiled, remove the container assembly from themicrowave and discharge the hot water in the container assembly (1).

Consequently, only the boiled pasta remains in the container assembly(1).

Thus, the container assembly (1) of the present invention may be usedfor boiling the food stuff easily.

Further, friction force between the protrusion (222) and the aperture(121) or their sizes may be designed so that the flap (22) upwardlyrotates when the inner pressure of the container assembly (1) exceeds apredetermined pressure. In this case, the container assembly (1) ofwhich the aperture (121) is plugged with the protrusion (222) of theflap (22) lying on the top of the container (21) can be put in themicrowave. For example, when the container assembly (1) containing agrain such as a potato is microwaved with closing the aperture (121),the potato can be boiled under a high pressure in the container assembly(1) so that the boiling time can be saved. In addition, when thepressure in the container assembly (1) exceeds the predetermined value,the flap (22) rotates upwardly so that the container assembly (1) willnot burst.

A fixing method of the cover (2) with the container (3) is notparticularly limited. The cover (2) formed in a cylindrical shape havinga threaded outer surface may be engaged with the container (3) having athreaded upper inner surface.

Alternatively, as shown in FIG. 12, an ear (29) configured to rotateupwardly and downwardly may be attached to the periphery of the cover(2), and the outer surface of the container (3) can be provided with aridge (39) configured to engage with an aperture (291) defined in acenter of the ear (29). Thus, the ear (29) and the protrusion (39) aremechanically engaged.

FIG. 13 is a cross-sectional view showing the container assembly (1)described in context with FIG. 1 to FIG. 6 in a stacking package.

The bottom of the container (3) comprises a peripheral area (35)defining the contour thereof and a central area (36) surrounded by theperipheral area (35). The central area (36) curves upwardly.

As described above, the peripheral area (211) of the cover (2) and theflap surrounding area (212) in the center of the cover (2) are elevatedwith respect to the intermediate area (213) connecting these areas (211,212).

When one container assembly (1) is placed on another container assembly(1), the flap surrounding area of the cover (2) is received in thecentral area (36) of the bottom of the container (3). Also, theperipheral area (35) of the bottom of the container (3) contacts withthe intermediate area (213) between the flap surrounding area (212) andthe peripheral area (211).

Thus, stable stacking of the container assemblies (1) can be achieved.

The present invention can be used as a container used with a cookingdevice for household use such as a microwave.

What is claimed is:
 1. A cover for covering an opening of a containerfor heating a food stuff, the cover comprising: an elevated peripheralportion defining an outer contour of the cover and configured to engagewith an edge of the container defining its opening; an elevated areasurrounded by and positioned apart from the elevated peripheral portion,the elevated area being lower than the peripheral portion; a pluralityof air vent ports defined in the elevated area; at least one flapincluding a proximal end integrally connected to an edge of the elevatedarea, the at least one flap configured to rotate around the proximalend; at least one protrusion extending from a first surface of the atleast one flap and configured to plug at least one of the plurality ofair vent ports when the flap reaches a first position where the at leastone flap is received in a concave area defined in the elevated area; anda groove defined at the proximal end in the first surface of the atleast one flap wherein a second surface opposite to the first surface atthe proximal end is straight when the flap stands upright to the concavearea.
 2. The cover in claim 1, wherein the second surface of the atleast one flap does not protrude from a surface of the elevated areawhen the at least one flap reached a first position.
 3. The cover inclaim 1, wherein the cover is not deformed under a thermal conditionless than 140 degrees centigrade.
 4. The cover in claim 1, wherein thecover is molded from a high crystallinity polypropylene.
 5. The cover inclaim 1 further comprising a tab protruding outwardly from a peripheraledge of the cover.
 6. The cover in claim 1, wherein the proximal end ofthe at least one flap is located farther away from a center of the coverthan a distal end of the flap.
 7. The cover in claim 1, wherein: theelevated area includes a concave portion adjacent to the concave area;and a distal end of the flap partly covers across the concave portionwhen the at least one flap reaches the first position.
 8. The cover ofclaim 1, further comprising an intermediate area connecting the elevatedperipheral portion and the elevated area, the intermediate area beinglower than the elevated area and surrounding the elevated area.
 9. Acontainer assembly for heating a food stuff comprising a containerincluding a bottom and at least one side wall surrounding the bottom,and a cover for covering an opening of the container comprising: anelevated peripheral portion defining an outer contour of the cover andconfigured to engage with an edge of the container defining its opening;an elevated area surrounded by and positioned apart from the elevatedperipheral portion, the elevated area being lower than the peripheralportion; a plurality of air vent ports defined in the elevated area ofthe cover; at least one flap including a proximal end integrallyconnected to an edge of the elevated area, the at least one flapconfigured to rotate around the proximal end; at least one protrusionextending from a first surface of the at least one flap and configuredto plug at least one of the plurality of air vent ports when the flapreaches a first position where the at least one flap is received in aconcave area defined in the elevated area; and a groove defined at theproximal end in the first surface of the at least one flap wherein asecond surface opposite to the first surface at the proximal end isstraight when the flap stands upright to the concave area.
 10. Thecontainer assembly in claim 9, wherein the second surface of the atleast one flap does not protrude from a surface of the elevated areawhen the at least one flap reached a first position.
 11. The containerassembly in claim 9, wherein the cover is not deformed under a thermalcondition less than 140 degrees centigrade.
 12. The container assemblyin claim 9, wherein the cover is molded from a high crystallinitypolypropylene.
 13. The container assembly in claim 9, further comprisinga tab protruding outwardly from a peripheral edge of the cover.
 14. Thecontainer assembly in claim 9, wherein the proximal end of the at leastone flap is located farther away from a center of the cover body than adistal end of the flap.
 15. The container assembly in claim 9, wherein:the elevated area includes a concave portion adjacent to the concavearea; and a distal end of the at least one flap partly covers across theconcave portion when the at least one flap reaches the first position.16. The container assembly in claim 9, further comprising: a partitionconfigured to divide an inner space of the container into a plurality ofcompartments; and wherein the at least one flap includes a plurality offlaps; the plurality of air vent ports is configured to communicate withthe plurality of compartments, respectively; and each of the pluralityof flaps closes at least one of the plurality of air vent port with theprotrusion.
 17. The container assembly in claim 9, wherein the coverincludes an intermediate area connecting the elevated peripheral portionand the elevated area, the intermediate area being lower than theelevated area and surrounding the elevated area.
 18. A containerassembly for heating a food stuff, the container assembly comprising: acontainer including a bottom, at least one side wall surrounding thebottom, and a partition configured to divide an inner space of thecontainer into a plurality of compartments; and a cover for covering anopening of the container, the cover comprising an elevated peripheralportion defining an outer contour of the cover and configured to engagewith an edge of the container defining its opening, an elevated areasurrounded by and positioned apart from the elevated peripheral portion,the elevated area being lower than the peripheral portion, a pluralityof air vent ports defined in the elevated area and configured tocommunicate with the plurality of compartments, respectively, aplurality of flaps, each flap including a proximal end integrallyconnected to an edge of the elevated area and being configured to rotatearound the proximal end, at least one protrusion extending from a firstsurface of each of the plurality of flaps, the protrusion beingconfigured to plug one of the plurality of air vent ports when the flapreaches a first position where the flap is received in a concave areadefined in the elevated area, and a groove defined at the proximal endin the first surface of each of the plurality of flaps, wherein a secondsurface opposite to the first surface at the proximal end is straightwhen the flap stands upright to the concave area.
 19. The containerassembly in claim 18, wherein the second surface of at least one of theplurality of flaps does not protrude from a surface of the elevated areawhen the flap reached a first position.
 20. The container assembly inclaim 18, wherein the cover is not deformed under a thermal conditionless than 140 degrees centigrade.
 21. The container assembly in claim18, wherein the cover is molded from a high crystallinity polypropylene.22. The container assembly in claim 18, further comprising a tabprotruding outwardly from a peripheral edge of the cover.
 23. Thecontainer assembly in claim 18, wherein the proximal end of at least oneof the plurality of flaps is located farther away from a center of thecover than a distal end of the flap.
 24. The container assembly in claim18, wherein: the elevated area includes a concave portion adjacent tothe concave area; and a distal end of at least one of the plurality offlaps partly covers across the concave portion when the flap reaches thefirst position.
 25. The container assembly in claim 18, wherein thecover includes an intermediate area connecting the elevated peripheralportion and the elevated area, the intermediate area being lower thanthe elevated area and surrounding the elevated area.